This invention relates to cartridge based data storage systems. More particularly, the invention relates to a cartridge based tape storage system that accepts a variety of cartridges having different physical dimensions.
Cartridge based tape and disk data storage devices have been in use in the computer industry for several decades. Primarily, the cartridge based tape storage devices have been used as sequential access devices, whereby new files are added to the tape by appending them to the last file stored on the tape. During that time, a number of tape cartridge styles emerged. One popular cartridge style is based on a design that is disclosed in U.S. Pat. No. 3,692,255 (Von Behren). That design employs two rotatable reels that are fixed within a rectangular housing. A length of tape is wound around the reels along a predetermined tape path, which extends along a front peripheral edge of the cartridge and across a tape access opening. A drive belt extends around drive belt rollers and contacts a portion of the tape on each reel to move the tape back and forth between the reels and across the tape access opening. A drive puck, positioned near the inside front of the cartridge, contacts a drive roller, which provides a mechanism to move the drive belt.
Tape cartridges and tape drives have become an increasingly important feature in computer systems. The popularity of tape cartridges is driven in part by the large storage capacities and low cost of storage they provide. In general, the storage capacity of a particular tape cartridge is dictated by a variety of factors including the length of tape, the width of the tape, the materials used to produce the tape and the recording density of the tape. Even with the cost and capacity advantages offered by tape storage solutions, the tape drive has primarily found use in computer systems as a back-up device, in which duplicates of files that were originally stored to a random access storage device, such as a hard disk drive, are stored for sequential access on a tape cartridge.
As with most popular computer devices, tape drives and cartridges evolved around industry standards. However, while standards can provide advantages such as compatibility they also bring design constraints. In particular, standards can impose constraints on the available design options used to increase storage capacity. For example, an early tape cartridge design standardized around a 51/4 inch form factor with a quarter inch tape width. As a result, storage capacity became constrained by the tape width and the length of tape that could fit within the 51/4 standard cartridge. Thus, other methods, such as improved recording densities, were needed to increase storage capacity.
All of the tape cartridges adhering to the original 51/4 inch standard had a number of physical characteristics in common to allow a particular tape to inter-operate among tape drives made by different manufacturers. For example, a tape access opening must be located in a particular location on the front of the tape cartridge to allow the read-write head to gain access to the tape. Additionally, the tapes employ an elastic belt that is wound around the tape spools to provide the tape movement, and a drive puck is provided to translate drive power to the belt. Accordingly, the puck must be in a standard fixed location to receive rotational power from standard drives.
As techniques were developed for increasing the recording density, the storage capacity of a given cartridge could be increased. Ultimately, recording densities continued to increased and a demand arose for a more convenient form factor, resulting in a new tape cartridge and drive standard. The new standard evolved around a smaller, 31/2 inch form factor. As with the earlier 51/4 standard, the 31/2 inch form factor required predefined head access opening locations and so on.
Even after the 31/2 inch form factor became the form factor of choice for many computer users, the need for increased capacity continued to develop. In response to the increasing demands for capacity in a 31/2 inch form factor, manufacturers developed a variety of cartridge geometries that adhered to the key compatibility aspects of the 31/2 inch cartridge, such as head access location, but which provided additional tape capacity within a given cartridge. For example, U.S. Pat. Nos. 5,543,992 (Hu et al.) and 5,543,992 (Anderson et al.) each describe some of the more popular developments that have been used to increase the tape capacity of 31/2 inch tape cartridges.
The Hu patent discloses a tape cartridge that increases tape length by increasing the interior volume of the tape cartridge and consequently the amount of space available for tape storage. Hu discloses a tape cartridge with a width and a tape interface that conform to the standard 31/2 inch form factor tape cartridges. However, the length of the Hu cartridge is more than twice the length of an original 31/2 inch tape cartridge. As a result, the Hu cartridge can contain up to four time the amount of tape as a conventional 31/2 inch cartridge. A tape cartridge of this general form factor is manufactured by Gigatek Memory Systems, Carlsbad, Calif. A competing tape with a similar form factor is available under the TR-3 Extra brand name and is manufactured by Verbatim Corporation. For clarity, cartridges of this type will be referred to herein as extended mini-catridges.
The tape cartridge design disclosed in the Anderson patent takes a somewhat different approach from the Hu approach to expanding the amount of available tape within the tape cartridge. Anderson keeps the front portion of the cartridge width substantially the same as a standard 31/2 inch mini cartridge and maintains the general tape interface configuration. However, the Anderson cartridge provides for both a wider and longer cartridge, though not as long as the extended mini-cartridge. By keeping the tape interface portion of the Anderson cartridge substantially the same as a standard 31/2 inch mini-cartridge, tape drives can be produced that are capable of reading both the standard 31/2 inch mini cartridge and the Anderson mini cartridge. A cartridge of this type is sold commercially under the TRAVAN.TM. brand name and is produced by 3M corporation. Notably, tape drives designed to accept the TRAVAN.TM. cartridges are also capable of accepting a standard 31/2 inch mini cartridge and, in many cases, can also accept an extended mini-cartridge.
The Anderson tape system provides for a tape drive that accepts cartridges that have two different widths. Purportedly providing a structure that supports two different width sizes, the Anderson tape drive accepts different cartridges so long as the cartridges have head access openings and drive pucks in predefined locations. Accordingly, such a drive is commercially available that accepts TRAVAN.TM. style cartridges as well as other narrow 31/2 inch mini-cartridges. However, a tape drive designed to read only standard (narrow) 31/2 inch mini-cartridges is generally not capable of accepting a TRAVAN.TM. cartridge because of the TRAVAN.TM. cartridge width. But because the extended min-cartridge keeps the width of the mini-cartridge consistent with the width of a standard cartridge, a tape drive capable of reading a standard mini-cartridge would likely be able to accept an extended mini-cartridge as well.
In recent years, the TRAVAN.TM. style cartridge has become a very popular tape cartridge form factor. Accordingly, many of the commercially available tape drives are capable of accepting any of the three cartridge formats (i.e., standard 31/2 inch mini cartridge, TRAVAN.TM. style mini cartridge and extended mini-cartridge). Cartridges according to the extended mini-cartridge form factor are generally capable of containing the most tape.
Although currently available tape drives, including drives incorporating the Anderson design, may accept a variety of tape cartridge form factors, they still have several significant drawbacks. For example, when used in connection with the extended mini-cartridge, the current tape drives present what has been referred to as the "tongue". That is, the extended mini-cartridge protrudes from the front of the tape drive. The tongue is not only unsightly, but is also undesirable for functional reasons. For example, when installed in a computer bay, an extended mini-cartridge may require several extra inches of clearance space. Unfortunately, this drawback of currently available tape drives has hindered the use of extended mini-cartridges and, consequently, the availability of higher storage capacities.
Therefore, there is a need for an improved tape drive that offers advantages over the prior art. The present invention provides such a tape drive.